It is common knowledge that paint cans of sizes up to at least one gallon are made with a circular groove lip seal that mates with a disc-shaped lid having a circular tongue that press fits into the groove to produce a tight seal. In custom paint blending shops any shade of color is available by mixing, according to a formula, two or more standard tints sold by the paint manufacturer. This normally requires the use of a new paint can which is thrown away after the consumer uses the paint. Since paint cans represent a substantial expense, it would be desirable to find a way to use such cans more than once, and it is an object of this invention to provide a system whereby such can be accomplished.